import java.util.Scanner;

public class Test {
    //杨辉三角的变形
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while(scanner.hasNext()){
            int n = scanner.nextInt();
            if(n <= 2){
                System.out.println("-1");
            }else if(n % 2 == 1){
                System.out.println("2");
            }else if(n % 4 == 0){
                System.out.println("3");
            }else{
                System.out.println("4");
            }
        }
    }
}
